Over one million Americans each year suffer from damage or injury to the central nervous system (ie. head injury, stroke, and brain tumors). In addition, diseases related to aging such as presenile dementia and Alzheimer's Disease are becoming a serious health problem. One of the major goals of basic and clincial research in the Neurosciences is to find new ways to improve recovery and the quality of life. The proposed project provides a means of studying the unique process of neurogenesis and nerve cell replacement that takes place in the mammalian olfactory system. Procedures will be used to induce degeneration of sensory neurons. Subsequent neurogenesis and recovery will be studied using quantitative methods to determine the capacity and limits of this process. Experiments are planned to determine the ability of replacement neuronsto reestablish connections with the central nervous system and restore function. In addition, a group of old animals will be studied to determine if the capacity for neurogenesis and recovery continues into old age. A technique developed for transplanting olfactory neurons into different regions of the CNS will be used to determine the capacity of these neurons to survive in host brain tissue. The persistence of neurogenesis within transplants and the growth of axons into the host brain could hve signficant impact on the field of regeneration. It is expected that data from the proposed study will produce new information about mechanism of neurogenesis and recovery following nerve cell injury. Potentially these studies may lead to methods for the repair of damaged pathways in the human central nervous system.